摘要
闽中地区马面山群沿政和一大埔断裂带分布。对马面山群3个标准剖面的变质岩样品进行了Sm-Nd同位素年龄测定,结果为:t=17.3～17.8亿年,ε_(Nd)(t)=+7.6～+7.8。研究表明:马面山群变质火山岩的形成时代为中元古宙而非加里东时期;政和一大埔断裂带为一长期存在、多阶段演化发展的构造单元。早期具克拉通上裂谷性质,为一发展不全的夭折裂谷。马面山群是华夏古陆上裂谷环境的产物。中元古宙(1.7～1.8Ga)高度亏损地幔(ε_(Nd)(t)=+7.6～+7.8)的出现,再次证明了华夏古陆(大量古元古宙一新元古宙地壳)的存在。
The Mamianshan Group in the middle part of Fujian Province is developed along the
Zhenghe-Dapu deep fault zone which is an important geological boundary in Fujian and even in
South China. Dating and study on genesis of the Mamianshan Group are important approach to
characterize the Zhenghe-Dapu deep fault zone, and to better understand the formation and evolu-
tion of the Cathaysia block.
Samples collected from three sections yield three isochrons with consistent ages within error
ranging from 1.73～1.77 Ga and with high initial ε_(Nd) ( t ) values. This suggests that the Mamian-
shan metamorphic basic volcanic rocks were formed in the Mesoproterozoic rather than in the
Caledonian period. This also suggests that the Zhenghe-Dapu deep fault zone was active as early as
in the Mesoproterozoic when it was a premature rift zone and that the Mamianshan meta-volcanic
rocks were products of the rifting in the Cathaysia. The high initial ε_(Nd) ( t ) values ( + 7.6
+ 10.9) of the Mamianshan meta-volcanic rocks suggest that they were derived from highly de-
pleted mantle. This implies that this mantle produced large amount of crustal matters before the
Mesoproterozoic probably in the Paleoproterozoic, which supports the existence of Cathaysia with
main Paleoproterozoic crust most of which was later destroyed or reworked.
出处
《高校地质学报》
CAS
CSCD
2003年第4期566-572,共7页
Geological Journal of China Universities
基金
国家自然科学基金(批准号:49672112)
教育部"跨世纪优秀人才计划"资助
